SPFの守備を上達する方法 – サポート

Last update: June, 28th 2022

Microsoft does not take any action in case of an SPF fail. Set up a stricter processing on EOP for a better protection.

SPF, or Sender Policy Framework, is a method to validate that an email may be sent from a specific domain (from declared host or IP).

When the IP address of a sender and their SPF don't match (SPF fail, TempError or PermError), their emails still end up in your inbox by default. For a better protection when receiving an email, you can choose to set up a stricter filtering method by updating your filtering policy.

Sending message to Junk folder

1. Log in to Microsoft 365 Defender.

2. Go to ポリシーとルール > click 脅威ポリシー > スパム対策ポリシー.

3.Click on 迷惑メール対策の受信ポリシー (既定).

4. In section バルクメールのしきい値とスパムのプロパティ click on スパムのしきい値とプロパティを編集する.

5. Turn the SPF レコード: ハードフェイル toggle on and click 保存.

After a few minutes, your emails will be moved to junk folder whenever the IP address and the SPF don't match.

Strict reject

If you want to respect the SPF RFC, a reject must be made if there's a PermError or a SPF fail result. To be strict on such result, you have to add a mail flow.

1. Log in to Microsoft 365 admin center and click すべて表示 > Exchange in the left menu.

2. Click メールフロー > ルール, then ルールの新規作成....

3. Select その他のオプション... and open the box in このルールを適用する条件....

4. Add a name for the rule and select メッセージヘッダー > 次のテキストパターンと一致する in the このルールを適用する条件... drop-down menu.

You will see this:

5. Click the テキストの入力... link in the text on the right. You will have the ヘッダー名の指定 box opening. Add value Received-SPF and click OK.

6. Click the テキストパターンの入力... link. In the 単語または語句の指定 box, add the word fail and click OK.

You should see this for the moment:

7. In the 実行する処理... section, select メッセージをブロックする... > メッセージを拒否してその説明を含める

In the box, add a reject reason like SPF fail for example and click OK.

Just save the rule clicking on 保存. After a few minutes, your emails will be deleted whenever the IP address and the SPF don't match.

Sending message to Junk folder

Strict reject

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